Corrosion of Alloy 625 in High-Temperature, High-Pressure Sulfate Solutions

摘要: Abstract Corrosion phenomena, of alloy 625 (UNS N06625) were investigated in oxygenated aqueous solutions containing sulfuric acid (H2SO4), sodium hydrogen sulfate (NaHSO4), or (Na2SO4) and deaerated H2SO4 solution. Tests conducted at temperatures pressures up to 500°C 38 MPa, respectively. the acidic solution started ∼ 150°C with intergranular attack (IGA). Above 250°C, whole surface was attacked, shallow pits deep IGA appeared. This behavior explained by transpassive dissolution protecting Cr(III) oxide layer. Severe material loss occurred between 300°C 390°C. At higher temperatures, only weak corrosion detected, probably because lower density phenomena NaHSO4 comparable but less severe than H2SO4. In Na2SO4 solutions, no observed maximum test temperature 350°C. oxygen-free l...